It's been recognized that duct mountable ambient condition detectors can be useful in ambient condition monitoring systems, such as fire detection systems. Such detectors, which might respond to airborne smoke or gases, can be coupled to ducts which might be part of an HVAC which extends through a building or region being monitored. Such detectors are disclosed for example in Berneau et al., U.S. Pat. No. 6,124,795 entitled Detector Interconnect System which issued Sep. 26, 2000, and which is assigned to the assignee hereof, as well as Fenne Design Pat. DES. 327,228 which issued Jun. 23, 1992, and is also assigned to the assignee hereof. The '795 and '228 patents are incorporated herein by reference.
Known duct detectors require one or more tubular conduits to redirect air from inside the associated duct, part of a building ventilation system, to the detector. The conduits or sampling tubes are formed with openings aligned along their length. The openings allow air to flow down the tube to the detector and return again to the system.
To ensure proper operation of the detector the openings must be aligned with the oncoming flow inside the system. The conduit must therefore be coupled to the detector housing or enclosure in a way that provides correct alignment and is secure to prevent disengagement or movement after installation.
Known configurations used to couple the conduits to detector housings or enclosures tend to be cumbersome and time consuming to install. Fasteners are often used to retain the sampling tubes. These usually require the use of hand tools and can be difficult to work with in the small dark spaces the detectors are frequently installed. Often the detector cover must be removed to install the tubes and gain access to the fasteners, adding to the time and effort required for installation. Should the sampling tubes be installed in the wrong position the cover must again be removed to release the tube and reposition it correctly.
One known coupling device is a formed flange fitted around the outer diameter of the conduit and fixed in place by a weld or a fastener as illustrated in FIGS. 1A & 1B. Another is a rectangular tab formed into the end of the conduit that is guided through slots and aligned with notches in the detector housing as in FIG. 2.
Both of the configurations of FIGS. 1A, 1B and 2 have disadvantages. Specialized production equipment is required to attach a separate flange or punch and form a tab. The equipment can be costly to purchase, require frequent maintenance, and may have high operating cost. A formed tab protruding from the end of the tube may be sharp and could injure an operator producing the tubes or a technician handling them during installation. An improved coupler design which eliminates the need for fastening or welding and utilizes less costly production equipment would be desirable.
Many man-hours could be saved and installation costs reduced if the coupling of these tubes was simple, quick, and did not require the use of tools or removal of the detector cover. In addition, insertion from both sides would be desirable.
HVAC systems used to condition air-within a building and often contain cooling coils, and humidifiers which expose the detector and sampling tubes to moisture. Condensation on the any surface of the sampling tubes could collect inside the detector and cause the detector to malfunction. Current sampling tube designs do little to prevent condensation from entering the detector enclosure. It would be desirable to provide a coupler that would route small amounts of moisture away from the detector and prevent accumulation in the enclosure.